FIFO question

FIFO question

[Eric Bambach]

Hello,
 
 This is the first time I am using named pipes. I have a process with this C++ 
code that creates a named pipe and loops on writing the character "2" to it.

stringstream ssbuffer;
string buffer;
int pipeFD;

while (true){
    pipeFD = open("my_pipe", O_WRONLY);
    ssbuffer << 2;
    buffer = ssbuffer.str();
    write( pipeFD, buffer.c_str(), 1 );
    close(pipeFD);
  }

 It happily sits on the pipe. When I open up another console and type "cat 
my_pipe" it prints an arbitrary number of 2s. Usually many tens of them. From 
what I read I thought that when I close the pipe using the close() call then 
the readers will quit. Furthermore the main program doesnt receive a broken 
pipe after the reader quits like it should. This is test code and I want just 
ONE "2" to be read by cat. Perhaps I am missing something simple? Can anyone 
enlighten me?

I plan to have only one reader and one writer on the pipe at a time so 
synchronization is not neccesary.

I have also tried nanosleeping after the close. It seems sleep(1) fixes the 
problem, but the main program still doesnt get a broken pipe after cat exits 
and this causes an unacceptable and unpredicate delay before the start of the 
read.

Futhermore I have also tried writing a very simple read program that tries to 
read 10 bytes from the FIFO. It succeeds and actually gets 10 bytes from the 
FIFO! Shouldnt the read be short because the main program called close after 
1 byte?

----------------------------------------
--EB

> All is fine except that I can reliably "oops" it simply by trying to read
> from /proc/apm (e.g. cat /proc/apm).
> oops output and ksymoops-2.3.4 output is attached.
> Is there anything else I can contribute?

The latitude and longtitude of the bios writers current position, and
a ballistic missile.

                --Alan Cox LKML-December 08,2000 

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Re: FIFO question

[Eric Bambach]

Fixed it.

On Thursday 06 January 2005 06:27 am, Eric Bambach wrote:
> Hello,
>
>  This is the first time I am using named pipes. I have a process with this
> C++ code that creates a named pipe and loops on writing the character "2"
> to it.
 ---snip---

----------------------------------------
--EB

> All is fine except that I can reliably "oops" it simply by trying to read
> from /proc/apm (e.g. cat /proc/apm).
> oops output and ksymoops-2.3.4 output is attached.
> Is there anything else I can contribute?

The latitude and longtitude of the bios writers current position, and
a ballistic missile.

                --Alan Cox LKML-December 08,2000 

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